1. Field of the Invention
The invention relates to an apparatus with retrievable setting means for running and setting a liner in a well bore casing.
2. Prior Art
The majority of prior art hydraulically set liner hangers have hydraulic setting mechanisms which are integral parts of the hanger assemblies and are left in the well following setting of the liner. The hydraulic setting mechanisms generally consist of piston-cylinder arrangements which, as part of the liner hanger, tend to restrict the I.D. of the well below the liner hanger. Moreover, since the setting mechanisms are integral parts of the liner hangers, they must remain in the well which greatly increases the cost of a liner hanger.
U.S. Pat. No. 4,096,913 discloses a running and setting tool in which its operating parts are retrievable. However, it provides both a hydraulic and mechanical setting means and therefore, requires the use of a drag block located below a J-slot assembly with the latter connected to the running tool by a shear pin. The function of the shear pin is to prevent any unintentional and premature setting of the liner hanger but because the drag block is in continuous contact with the casing as the tool is run into the hole, the frictional force created by this contact is transmitted directly to the shear pin which could cause the shear pin to sever while the tool is being lowered into the hole resulting in premature setting of the liner hanger. Additionally, drag forces created between the liner and liner hanger and the well bore and well bore casing is also transmitted directly to the shear pin which could similarly cause premature setting of the liner hanger.
Also, since both hydraulic and mechanical setting means are included on the running tool, the running tool is very complicated and expensive.